Light emitting device and method for manufacturing the same

ABSTRACT

A light emitting device comprises a second electrode layer; a second conductivity-type semiconductor layer on the second electrode layer; a current blocking layer comprising an oxide of the second conductivity-type semiconductor layer; an active layer on the second conductivity-type semiconductor layer; a first conductivity-type semiconductor layer on the active layer; and a first electrode layer on the first conductivity-type semiconductor layer.

This application is a Continuation of co-pending application Ser. No.12/433,464 filed on Apr. 30, 2009, which claims priority to KoreanPatent Application No. 10-2008-0040672, filed on Apr. 30, 2008, KoreanPatent Application No. 10-2008-0042601, filed on May 8, 2008, and KoreanPatent Application No. 10-2008-0042603, filed on May 8, 2008. The entirecontents of all of the above applications are hereby incorporated byreference.

BACKGROUND

The present disclosure relates to a light emitting device and a methodfor manufacturing the same.

Recently, many studies have been conducted on devices that use lightemitting diodes (LEDs) as light emitting devices.

An LED is a device that converts an electric signal into light by usingcharacteristics of compound semiconductors. An LED has a stackedstructure with a semiconductor layer of a first conductivity type, anactive layer, and a semiconductor layer of a second conductivity type,and emits light from the active layer when a voltage is applied. Thefirst conductivity-type semiconductor layer may be an n-typesemiconductor layer and the second conductivity-type semiconductor layermay be a p-type semiconductor layer, and vice versa.

Meanwhile, in a vertical LED structure where a first electrode layerapplying a voltage to the first conductivity-type semiconductor layerand a second electrode layer applying a voltage to the secondconductivity-type semiconductor layer are arranged in a verticaldirection, electric current may not flow in a wide area and may flowwith concentration on a lower side of the first electrode layer. If theelectric current flows with concentration on a specific region, anoperating voltage may increase to lower the intensity of light, thusdegrading the reliability of the light emitting device.

Furthermore, there is a need to improve light extraction efficiency sothat light emitted from the active layer is effectively extracted to theoutside.

SUMMARY

Embodiments provide a light emitting device having a new structure, anda method for manufacturing the same.

Embodiments also provide a light emitting device having improved lightextraction efficiency, and a method for manufacturing the same.

Embodiments also provide a light emitting device capable of suppressingelectric current from flowing with concentration on a specific region,and a method for manufacturing the same.

Embodiments also provide a light emitting device capable of operating astable driving voltage, and a method for manufacturing the same.

In an embodiment, a light emitting device comprises: a second electrodelayer; a second conductivity-type semiconductor layer on the secondelectrode layer; a current blocking layer comprising an oxide of thesecond conductivity-type semiconductor layer; an active layer on thesecond conductivity-type semiconductor layer; a first conductivity-typesemiconductor layer on the active layer; and a first electrode layer onthe first conductivity-type semiconductor layer.

In an embodiment, a light emitting device comprises: a second electrodelayer; a second conductivity-type semiconductor layer on the secondelectrode layer; an active layer on the second conductivity-typesemiconductor layer; a first conductivity-type semiconductor layer onthe active layer; a current blocking layer in the firstconductivity-type semiconductor layer; and a first electrode layer onthe first conductivity-type semiconductor layer.

In an embodiment, a light emitting device comprises: a second electrodelayer; a second conductivity-type semiconductor layer on the secondelectrode layer; an active layer on the second conductivity-typesemiconductor layer; a first conductivity-type semiconductor layer onthe active layer, the first conductivity-type semiconductor layercomprising a first nitride layer and a second nitride layer; and a firstelectrode layer on the first conductivity-type semiconductor layer.

BRIEF DESCRIPTION OF THE DRAWINGS

FIGS. 1 to 6 are sectional views explaining a light emitting device anda method for manufacturing the same according to a first embodiment.

FIG. 7 is a sectional view explaining a light emitting device accordingto a second embodiment.

FIG. 8 is a sectional view explaining a light emitting device accordingto a third embodiment of the present invention.

FIGS. 9 to 15 are sectional views explaining a light emitting device anda method for manufacturing the same according to a fourth embodiment.

FIG. 16 is a sectional view explaining a light emitting device accordingto a fifth embodiment.

FIG. 17 is a plan view of a current blocking layer illustrated in FIG.15.

FIG. 18 is a plan view of a current blocking layer illustrated in FIG.16.

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS

In the following description, it will be understood that when a layer(or film) is referred to as being “on” another layer or substrate, itcan be directly on the other layer or substrate, or intervening layersmay also be present. Further, it will be understood that when a layer isreferred to as being “under” another layer, it can be directly under theother layer, and one or more intervening layers may also be present. Inaddition, it will also be understood that when a layer is referred to asbeing “between” two layers, it can be the only layer between the twolayers, or one or more intervening layers may also be present.

In the drawings, the thicknesses of layers and regions are exaggeratedfor clarity. Also, the size of each element does not entirely reflect anactual size.

Hereinafter, light emitting devices and methods for manufacturing thesame according to embodiments will be described in detail with referenceto the accompanying drawings.

FIGS. 1 to 6 are sectional views explaining a light emitting device anda method for manufacturing the same according to a first embodiment.

Referring to FIG. 6, the light emitting device according to the firstembodiment includes a second electrode layer 90, an ohmic contact layer80 on the second electrode layer 90, a second conductivity-typesemiconductor layer 50 on the ohmic contact layer 80, an active layer40, a first conductivity-type semiconductor layer 30, and a firstelectrode 100 on the first conductivity-type semiconductor layer 30.

Also, a current blocking layer 70 for changing a current path isdisposed on the second conductivity-type semiconductor layer 50.

A bottom surface and a side surface of the ohmic contact layer 80 may bein contact with the second electrode layer 90. A top surface of theohmic contact layer 80 and a top surface of the second electrode layer90 may be disposed on the same horizontal plane.

The first electrode layer 100 and the ohmic contact layer 80 aredisposed in a vertical direction. The first electrode layer 100 and thesecond electrode layer 90 may be disposed in a vertical direction. Thatis, at least portions of the first electrode layer 100 and the ohmiccontact layer 80 or the second electrode layer 90 may be disposed on thesame vertical plane.

In the light emitting device according to the first embodiment, thecurrent blocking layer 70 is disposed inside the secondconductivity-type semiconductor layer 50. The current blocking layer 70may be disposed at a boundary between the second conductivity-typesemiconductor layer 50 and the ohmic contact layer 80. For example, atop surface and a side surface of the current blocking layer 70 may bein contact with the second conductivity-type semiconductor layer 50, anda bottom surface of the current blocking layer 70 may be in contact withthe ohmic contact layer 80.

The current blocking layer 70 may be formed of a material having aninsulating characteristic, and the current blocking layer 70 may beformed of oxide by oxidizing the second conductivity-type semiconductorlayer 50. The current blocking layer 70 may be formed of Ga_(x)O_(y),which is formed by a plasma oxidation process, and may have a thicknessof about 10 nm to about 100 nm.

As indicated by an arrow in FIG. 6, due to the formation of the currentblocking layer 70, the current flowing from the ohmic contact layer 80to the first electrode layer 100 does not concentrate on the lower sideof the first electrode layer 100, and flows in a wide area over thefirst conductivity-type semiconductor layer 30.

Therefore, it is possible to prevent the current concentrationphenomenon that the electric current flows with concentration on thelower side of the first electrode layer 100. Consequently, the lightemitting device can operate at a stable operating voltage and the lightemission efficiency can be improved.

Moreover, the first conductivity-type semiconductor layer 30 may includea first nitride layer 31 and a second nitride layer 32. The firstnitride layer 31 may be formed of a medium layer having a lowerrefractive index than the second nitride layer 32. In other words, thesecond nitride layer 32 may be formed of a medium layer having a higherrefractive index than the first nitride layer 31.

The first nitride layer 31 may be formed of Al_(x)Ga_(1-x)N (0<x≦1), forexample, n-AlGaN or n-AlN, and the second layer 32 may be formed ofn-GaN. When the wavelength of light emitted from the active layer 40 is450 nm, the refractive index of GaN is about 2.44 and the refractiveindex of AlGaN or AlN is about 2.12 to about 2.44.

The refractive index of AlGaN changes to about 2.12 to about 2.44according to a composition ratio of Al to Ga. When the content of Al isrelatively larger than that of Ga, the refractive index becomes lower,thus increasing the light extraction efficiency.

In the light emitting device according to the first embodiment, sincethe first conductivity-type semiconductor layer 30 includes the firstnitride layer 31 and the second nitride layer 32, light that is emittedfrom the active layer and incident onto the second nitride layer 32 canbe effectively extracted through the first nitride layer 31 to theoutside. Consequently, the light emission efficiency of the lightemitting device can be improved.

FIG. 7 is a sectional view of a light emitting device according to asecond embodiment, and FIG. 8 is a sectional view of a light emittingdevice according to a third embodiment.

The fundamental characteristics of the light emitting devices of FIGS. 7and 8 are similar to those of the light emitting device of FIG. 6.However, in the light emitting devices of FIGS. 7 and 8, the currentblocking layer 70 is modified in the position, size and number. Theposition of the first electrode layer 100 may be changed according tothe position, size and number of the current blocking layer 70.

In the embodiments, the current blocking layer 70 may be disposed in acentral region of the bottom surface of the second conductivity-typesemiconductor layer 50, or a region other than the central region.Furthermore, the current blocking layer 70 may have at least twodifferent sizes.

Hereinafter, a method for manufacturing a light emitting deviceaccording to a first embodiment will be described in detail withreference to FIGS. 1 to 6.

Referring to FIG. 1, an undoped GaN layer 20, a first conductivity-typesemiconductor layer 30, an active layer 40, and a secondconductivity-type semiconductor layer 50 are formed on a substrate 10. Abuffer layer (not shown) may be further formed between the substrate 10and the undoped GaN layer 20.

The substrate 10 may be formed of at least one of sapphire (Al₂O₃), Si,SiC, GaAs, ZnO, or MgO.

The buffer layer may include a multi-layer with a stacked structure suchas AlInN/GaN, In_(x)Ga_(1-x)N/GaN, andAl_(x)InyGa_(1-x-y)N/In_(x)Ga_(1-x)N/GaN. For example, the buffer layermay be grown by injecting trimethylgallium (TMGa), trimethylindium(TMIn), and trimethylaluminum (TMAl) into the chamber together withhydrogen gas and ammonia gas.

The undoped GaN layer 20 may be grown by injecting trimethylgallium(TMGa) into the chamber together with hydrogen gas and ammonia gas.

The first conductivity-type semiconductor layer 30 may be a nitridesemiconductor layer doped with impurity ions of the first conductivitytype, and the first conductivity-type semiconductor layer 30 may includea first nitride layer 31 having a low refractive index and a secondnitride layer 32 having a high refractive index.

The first conductivity-type semiconductor layer 30 may be asemiconductor layer doped with n-type impurity ions. The firstconductivity-type semiconductor layer 30 may be grown by injectingtrimethylgallium (TMGa), trimethylaluminum (TMAl), and silane gas (SiN₄)containing n-type impurities (for example, Si) into the chamber togetherwith hydrogen gas and ammonia gas.

The active layer 40 and the second conductivity-type semiconductor layer50 are formed on the first conductivity-type semiconductor layer 30.

The active layer 40 may be formed in a single quantum well structure ora multi-quantum well structure. For example, the active layer 40 may beformed in a stacked structure of an InGaN well layer/a GaN barrierlayer.

The second conductivity-type semiconductor layer 50 may be a nitridesemiconductor layer doped with impurity ions of the second conductivitytype. For example, the second conductivity-type semiconductor layer 50may be a semiconductor layer doped with p-type impurity ions. The secondconductivity-type semiconductor layer 50 may be grown by injectingbis(ethylcyclopentadienyl)magnesium (EtCp₂Mg){Mg(C₂H₅C₅H₄)₂} into thechamber together with hydrogen gas and ammonia gas.

Referring to FIG. 2, a mask 60 is formed on the second conductivity-typesemiconductor layer 50, and a current blocking layer 70 is selectivelyformed by O₂ plasma.

The current blocking layer 70 may be formed of oxide, for example,Ga_(x)O_(y). The current blocking layer 70 may be represented by thefollowing chemical formula.

4GaN+3O₂→2Ga₂O₃+2N₂

Meanwhile, the current blocking layer 70 may be formed as illustrated inFIG. 7 or 8 according to patterns of the mask 60.

Referring to FIG. 3, after forming the current blocking layer 70, themask 60 is removed.

Referring to FIG. 4, an ohmic contact layer 80 and a second electrodelayer 90 are formed on the second conductivity-type semiconductor layer50 and the current blocking layer 70.

The ohmic contact layer 80 may include a transparent electrode layer.For example, the ohmic contact layer 80 may be formed of at least one ofindium tin oxide (ITO), ZnO, RuO_(x), TiO_(x), or IrO_(x).

Also, the ohmic contact layer 80 may include at least one of areflective layer and an adhesive layer.

The second electrode layer 90 may be formed of at least one of copper(Cu), titan (Ti), chrome (Cr), nickel (Ni), aluminum (Al), platinum(Pt), gold (Au), or a conductive substrate.

Referring to FIG. 5, the substrate 10 and the undoped GaN layer 20 areremoved from the structure of FIG. 4. If the buffer layer has beenformed, the buffer layer is also removed.

Referring to FIG. 6, an isolation etching process for chip separation isperformed on the structure of FIG. 5.

A first electrode layer 100 is formed on the first conductivity-typesemiconductor layer 30. The first electrode layer 100 may be formed ofat least one of copper (Cu), titan (Ti), chrome (Cr), nickel (Ni),aluminum (Al), platinum (Pt), or gold (Au).

In this way, the light emitting device of FIG. 6 can be manufactured.

FIGS. 9 to 15 are sectional views explaining a light emitting device anda method for manufacturing the same according to a fourth embodiment.

Referring to FIG. 15, the light emitting device according to the fourthembodiment includes a second electrode layer 90, an ohmic contact layer80 on the second electrode layer 90, a second conductivity-typesemiconductor layer 50 on the ohmic contact layer 80, an active layer40, a first conductivity-type semiconductor layer 30, and a firstelectrode 100 on the first conductivity-type semiconductor layer 30.Also, a current blocking layer 70 for changing a current path isdisposed on the first conductivity-type semiconductor layer 30.

A bottom surface and a side surface of the ohmic contact layer 80 may bein contact with the second electrode layer 90. A top surface of theohmic contact layer 80 and a top surface of the second electrode layer90 may be disposed on the same horizontal plane.

The first electrode layer 100 and the ohmic contact layer 80 aredisposed in a vertical direction. The first electrode layer 100 and thesecond electrode layer 90 may be disposed in a vertical direction. Thatis, at least a portion of the first electrode layer 100 and the ohmiccontact layer 80 or the second electrode layer 90 may be disposed on thesame vertical plane.

In the light emitting device according to the fourth embodiment, thecurrent blocking layer 70 is disposed inside the first conductivity-typesemiconductor layer 30 under the first electrode layer 100. The currentblocking layer 70 is formed of an insulating material. The currentblocking layer 70 may be formed of at least one of SiO₂, SiN_(x), TiO₂,Ta₂O₃, SiOn, and SiCN.

As indicated by an arrow in FIG. 15, due to the formation of the currentblocking layer 70, the current flowing from the ohmic contact layer 80to the first electrode layer 100 does not concentrate on the lower sideof the first electrode layer 100, and flows in a wide area over thefirst conductivity-type semiconductor layer 30.

Therefore, it is possible to prevent the current concentrationphenomenon that the electric current flows with concentration on thelower side of the first electrode layer 100. Consequently, the lightemitting device can operate at a stable operating voltage and the lightemission efficiency can be improved.

Moreover, the first conductivity-type semiconductor layer 30 may includea first nitride layer 31 and a second nitride layer 32. The firstnitride layer 31 may be formed of a medium layer having a lowerrefractive index than the second nitride layer 32. In other words, thesecond nitride layer 32 may be formed of a medium layer having a higherrefractive index than the first nitride layer 31.

In this embodiment, the current blocking layer 70 is formed in thesecond nitride layer 32.

The first nitride layer 31 may be formed of Al_(x)Ga_(1-x)N (0<x≦1), forexample, n-AlGaN or n-AlN, and the second layer 32 may be formed ofn-GaN. When the wavelength of light emitted from the active layer 40 is450 nm, the refractive index of GaN is about 2.44 and the refractiveindex of AlGaN or AlN is about 2.12 to about 2.44.

The refractive index of AlGaN changes to about 2.12 to about 2.44according to a composition ratio of Al to Ga. When the content of Al isrelatively larger than that of Ga, the refractive index becomes lower,thus increasing the light extraction efficiency.

In the light emitting device according to the fourth embodiment, sincethe first conductivity-type semiconductor layer 30 includes the firstnitride layer 31 and the second nitride layer 32, light that is emittedfrom the active layer and incident onto the second nitride layer 32 canbe effectively extracted through the first nitride layer 31 to theoutside. Consequently, the light emission efficiency of the lightemitting device can be improved.

FIG. 16 is a sectional view of a light emitting device according to afifth embodiment.

The fundamental characteristics of the light emitting device of FIG. 16are similar to those of the light emitting device of FIG. 15. However,in the light emitting device of FIG. 16, the current blocking layer 70is partially provided in plurality.

When the current blocking layer 70 is partially provided in plurality,the first conductivity-type semiconductor layer 30 can be grown moreeasily.

Since the electric current also flows between the current blockinglayers 70, the current spreading effect can be maximized.

FIG. 17 is a plan view of the current blocking layer illustrated in FIG.15, and FIG. 18 is a plan view of the current blocking layer illustratedin FIG. 16.

As illustrated in FIGS. 15 and 16, the first conductivity-typesemiconductor layer 30 is also grown on the current blocking layer 70.As illustrated in FIG. 18, when the current blocking layer 70 is dividedinto a plurality of layers and spaced apart from one another, the firstconductivity-type semiconductor layer 30 can be grown between thecurrent blocking layers 70.

Hereinafter, a method for manufacturing a light emitting deviceaccording to a fourth embodiment will be described in detail withreference to FIGS. 9 to 15.

Referring to FIG. 9, an undoped GaN layer 20 and a firstconductivity-type semiconductor layer 30 are formed on a substrate 10. Abuffer layer (not shown) may be further formed between the substrate 10and the undoped GaN layer 20.

The substrate 10 may be formed of at least one of sapphire (Al₂O₃), Si,SiC, GaAs, ZnO, or MgO.

The buffer layer may include a multi-layer with a stacked structure suchas AlInN/GaN, In_(x)Ga_(1-x)N/GaN, andAl_(x)In_(y)Ga_(1-x-y)N/In_(x)Ga_(1-x)N/GaN. For example, the bufferlayer may be grown by injecting trimethylgallium (TMGa), trimethylindium(TMIn), and trimethylaluminum (TMAl) into the chamber together withhydrogen gas and ammonia gas.

The undoped GaN layer 20 may be grown by injecting trimethylgallium(TMGa) into the chamber together with hydrogen gas and ammonia gas.

The first conductivity-type semiconductor layer 30 may be a nitridesemiconductor layer doped with impurity ions of the first conductivitytype, and the first conductivity-type semiconductor layer 30 may includea first nitride layer 31 having a low refractive index and a secondnitride layer 32 having a high refractive index.

The first conductivity-type semiconductor layer 30 may be asemiconductor layer doped with n-type impurity ions. The firstconductivity-type semiconductor layer 30 may be grown by injectingtrimethylgallium (TMGa), trimethylaluminum (TMAl), and silane gas (SiN₄)containing n-type impurities (for example, Si) into the chamber togetherwith hydrogen gas and ammonia gas.

The first nitride layer 31 is formed on the undoped GaN layer 20, andthe second nitride layer 32 is grown on the first nitride layer 31 to apredetermined thickness.

Referring to FIG. 10, a mask (not shown) is formed on the second nitridelayer 32, and a current blocking layer 70 is formed of an insulatingmaterial. The current blocking layer 70 may be formed of at least one ofSiO₂, SiN, TiO₂, Ta₂O₃, SiON, and SiCN. For example, when the currentblocking layer 70 is formed of SiO₂, it can be formed through a CVDprocess by injecting silicon-containing gas such as SiH₄ or Si₂H₆ andoxygen-containing gas such as N₂O, O₂ or O₃.

In this case, the current blocking layer 70 may be formed as illustratedin FIGS. 10 and 17 or FIGS. 16 and 18 according to the pattern shapes ofthe mask (not shown).

Referring to FIG. 11, the mask (not shown) is removed, and the secondnitride layer 30 is additionally grown. As the second nitride layer 32is additionally grown, the current blocking layer 70 is buried withinthe second nitride layer 32.

An active layer 40 and a semiconductor layer 50 of a second conductivitytype are formed on the first conductivity-type semiconductor layer 30.

The active layer 40 may be formed in a single quantum well structure ora multi-quantum well structure. For example, the active layer 40 may beformed in a stacked structure of an InGaN well layer/a GaN barrierlayer.

The second conductivity-type semiconductor layer 50 may be a nitridesemiconductor layer doped with impurity ions of the second conductivitytype. For example, the second conductivity-type semiconductor layer 50may be a semiconductor layer doped with p-type impurity ions. The secondconductivity-type semiconductor layer 50 may be grown by injectingbis(ethylcyclopentadienyl)magnesium (EtCp₂Mg){Mg(C₂H₅C₅H₄)₂} into thechamber together with hydrogen gas and ammonia gas.

Referring to FIG. 12, an ohmic contact layer 80 and a second electrodelayer 90 are formed on the second conductivity-type semiconductor layer50.

The ohmic contact layer 80 may include a transparent electrode layer.For example, the ohmic contact layer 80 may be formed of at least one ofindium tin oxide (ITO), ZnO, RuO_(x), TiO_(x), or IrO_(x).

Also, the ohmic contact layer 80 may include at least one of areflective layer and an adhesive layer.

The second electrode layer 90 may be formed of at least one of copper(Cu), titan (Ti), chrome (Cr), nickel (Ni), aluminum (Al), platinum(Pt), gold (Au), or a conductive substrate.

Referring to FIG. 13, the substrate 10 and the undoped GaN layer 20 areremoved from the structure of FIG. 12. If the buffer layer has beenformed, the buffer layer is also removed.

Referring to FIG. 14, an isolation etching process for chip separationis performed on the structure of FIG. 13.

Referring to FIG. 15, a first electrode layer 100 is formed on the firstconductivity-type semiconductor layer 30. The first electrode layer 100may be formed of at least one of copper (Cu), titan (Ti), chrome (Cr),nickel (Ni), aluminum (Al), platinum (Pt), or gold (Au).

In this way, the light emitting devices of FIGS. 15 and 16 can bemanufactured.

Although embodiments have been described with reference to a number ofillustrative embodiments thereof, it should be understood that numerousother modifications and embodiments can be devised by those skilled inthe art that will fall within the spirit and scope of the principles ofthis disclosure. More particularly, various variations and modificationsare possible in the component parts and/or arrangements of the subjectcombination arrangement within the scope of the disclosure, the drawingsand the appended claims. In addition to variations and modifications inthe component parts and/or arrangements, alternative uses will also beapparent to those skilled in the art.

1. A light emitting device, comprising: a second electrode layer; asecond conductivity-type semiconductor layer on the second electrodelayer; an active layer on the second conductivity-type semiconductorlayer; a first conductivity-type semiconductor layer on the activelayer; a current blocking layer in the first conductivity-typesemiconductor layer; and a first electrode layer on the firstconductivity-type semiconductor layer.
 2. The light emitting deviceaccording to claim 1, wherein at least portions of the first electrodelayer, the second electrode layer, and the current blocking layer areoverlapped in a vertical direction.
 3. The light emitting deviceaccording to claim 1, wherein a top surface, a bottom surface, and aside surface of the current blocking layer are surrounded by the firstconductivity-type semiconductor layer.
 4. The light emitting deviceaccording to claim 1, wherein the current blocking layer is formed of atleast one of SiO₂, SiN_(x), TiO₂, Ta₂O₃, SiON, or SiCN.
 5. The lightemitting device according to claim 1, wherein the current blocking layeris provided in plurality and spaced apart from one another.
 6. The lightemitting device according to claim 1, wherein the firstconductivity-type semiconductor layer comprises a first nitride layerand a second nitride layer, and the first nitride layer has a smallerrefractive index than the second nitride layer.
 7. The light emittingdevice according to claim 6, wherein the current blocking layer isformed in the second nitride layer.
 8. The light emitting deviceaccording to claim 6, wherein the first nitride layer comprises an AlGaNlayer or an AlN layer, and the second nitride layer comprises a GaNlayer.